PENSION AND OTHER POSTRETIREMENT BENEFITS - Schedule of Defined Benefit Plans Disclosure (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 1,519	$ 974	$ 4,701	$ 4,349
Interest Cost	3,404	3,862	9,876	11,388
Expected Return on Plan Assets	(6,154)	(5,569)	(17,821)	(16,473)
Amortizations:
Prior Service Cost	25	26	73	79
Actuarial Loss	3,325	2,647	9,713	8,077
Net Periodic Benefit Cost	2,119	1,940	6,542	7,420
Capitalized Benefit Cost	(577)	(410)	(1,708)	(1,470)
Deferred Benefit Cost	(339)	(377)	(971)	(1,193)
Total Net Periodic Benefit Expense	1,203	1,153	3,863	4,757
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	212	182	638	511
Interest Cost	475	560	1,424	1,775
Expected Return on Plan Assets	(1,436)	(1,345)	(4,308)	(4,036)
Amortizations:
Prior Service Cost	(156)	(180)	(468)	(468)
Actuarial Loss	273	255	817	640
Net Periodic Benefit Cost	(632)	(528)	(1,897)	(1,578)
Capitalized Benefit Cost	(108)	57	(320)	(157)
Deferred Benefit Cost	337	(90)	1,010	701
Total Net Periodic Benefit Expense	$ (403)	$ (561)	$ (1,207)	$ (1,034)